A heat treatment apparatus in which semiconductor wafers (hereinafter, referred to as “wafers”) as a plurality of substrates are mounted on a rotary table in a rotational direction of the rotary table installed inside a processing vessel has been used. This heat treatment apparatus includes a gas supply part installed in the diameter direction of the rotary table to supply a processing gas and a heater installed below the rotary table to heat the wafers. In addition, the rotary table is rotated in a state where the gas is discharged from the gas supply part and the wafers are heated by the heater, so that each of the wafers is subjected to a film forming process.
In such a heat treatment apparatus, for example, a temperature control is performed using, as a wafer temperature, a temperature measured by a thermocouple (TC for heater control) installed near the heater.
A semiconductor manufacturing apparatus has also been used in which a temperature of a susceptor having wafers mounted thereon is measured using a radiation thermometer in a film forming process, and an output of a heater is controlled based on the measurement result, thereby performing the film forming process on the wafers.
However, the apparatus fails to accurately measure a temperature of the wafer in the film forming process which is performed while rotating the rotary table. This makes it difficult to perform the film forming process on the wafer by controlling the wafer to have an appropriate temperature.